Many abused drugs share a common, acute effect of increasing rates of social interaction, especially conversation. This capacity to facilitate social interaction could be an important component of the widespread appeal of abused drugs (i.e., reinforcing effects). To date, little is known about how or why this effect occurs. The present project will investigate the following hypothesis: Abused drugs facilitate social behavior by increasing the reinforcing efficacy of social interaction. To test this, acute doses of cocaine, d-amphetamine, alcohol, secobarbital and marijuana will be administered to volunteers using two experimental procedures: The first procedure is a two- component multiple schedule. In one component of the schedule, the opportunity to earn money will be available via a fixed-ratio schedule. In the other component of the schedule, the opportunity to socialize will be available via the same schedule. If our hypothesis is correct, response rates in the social component should increase as a function of drug. The selectivity of drug effects on social interaction will be assessed by comparing the effects of the drug on responding in the social and monetary components. The second procedure will be a discretetrial choice procedure. Subjects will make a series of mutually exclusive choices between the monetary and social conditions described above. If our hypothesis is correct, preference for the social option should increase as a function of drug. This grant will 1) provide new and important information on the mechanisms involved in the interaction of abused drugs and social behavior, 2) compare and contrast the effects of abused drugs on the reinforcing function of two important aspects of human behavior (socializing & earning money) and 3) improve our understanding of the relationship between behavioral and reinforcing effects of drugs.